Kepouros:
The dilute milk is, in fact, one of the organic remedies for plant mildews, along with baking soda solutions, and dilute human urine (4-1 ratio). Plant mildews live and spread on the surfaces of the plants (leaves stems, flowers etc), and while none of these remedies actually kills of the infection completely, all will act as controls which reduce the severity of the attack and delay the spread. However, they do not in fact produce any form of protective barrier.

Potato and tomato blights are entirely different type of fungi, in that the spores, having landed on the plant, immediately penetrate the surface and take up residence inside the plant where they cannot be attacked by any form of control other than systemic ones (of which there are none for blight).

The present protective treatments for blight are purely prophylactic in that they must be present before the blight spores arrive, they do not form a barrier to penetration, but work by killing or neutralising the blight spores which land on them, and they are usually effective only until the next shower of rain washes them off or dilutes them.

I doubt if dilute milk would have any effect whatever in protecting against potato or tomato blight, although in a really wet summer I doubt whether any of the methods available to amateurs have much effect anyway, and adoption of proper post infection procedures is of more value.

As to realfood`s suggestion, his treatment was many years ago the staple treatment for the Aspidistra, the rubber plant, the `swiss cheese` plant etc, but that was in the days when full cream milk came with an inch of rich yellow cream on the top which could be scooped off and whipped, or poured over the tinned peaches on Sundays, but I haven`t seen milk like that for very many years, and half of you probably won`t even know what I`m talking about.

PurpleHeather:
Gosh proper milk. The jersey milk still has a bit of a 'head' on it. It was the old 'gold top'. The only advantage of cream free milk is that it can be kept in the freezer.

Interesting read, good bacteria verses bad bacteria principle perhaps, using it as a blight cure. Surely, as it would be such a low cost simple cure, if it worked, every grower would have use it and blight would no longer be a problem anywhere.

There are some jokers who start rumours about 'cures' just to see who is daft enough to do it. By the time these rumours have done the chinese whisper tour they become certain tried and tested formulas. Especially if, after doing the daft deed, the grower gets good results (which they would have got anyway but do not realise it).

Digeroo:
I heard last year that Aloe Vera would help with blight on tomatoes. It did - those that had been treated lasted about a week longer than the rest. I might try yoghourt it works for human fungal infections.